[Openicc] new version of xcalib

[Ben Guthro]

On Mar 6, 2005, at 9:14 PM, Graeme Gill wrote:
>
>>>     DDC:
>
>> I don't agree on this. NEC published DDC/CI which is a add-on for the
>> DDC standard. Even for Linux we have rudimentary apps which support  
>> some
>> DDC features (contrast and other unnecessary items).
>
> Do you have a reference to the NEC document ? I found one on "NAVISET",
> but there was nothing directly about DDC/CI in it.
>
> I've noticed the Linix tools, but the impression I got was that they  
> had been
> implemented mostly by reverse engineering the wire protocol. It
> solves a particular problem, but it doesn't give you much confidence
> that it's going to work with all DDC compliant monitors out there.
> Of course it shows that access to DDC is available in Linux.
>

DDC/CI:
This is part of the VESA spec, and not a Naviset addition. However,  
NaviSet uses this standard.
The specific chapters that apply to the DDC command interface (DDC/ci)  
are chapter 2 of the spec (DDC/CI standard)
Unfortunately, this is not freely available from VESA. This standard is  
essentially a protocol working on top of the i2c bus, and therefore  
should be fairly easy to implement.

Someone has made some very good headway in this, using the i2c-dev  
interface in linux, though looking through his code, there are a few  
things he had to reverse engineer that don't quite match the spec  
exactly.

http://sourceforge.net/projects/ddccontrol

The VESA specs can be purchased here:
https://fs16.formsite.com/VESA/VESAForms/secure_index.html

Many of the enumerations for the VCP commands have been duplicated in  
the Monitor section of USB HID control. This can be found here:
http://www.usb.org/developers/devclass_docs/usbmon10.pdf



>>  I don't like it as well, that the specs
>> aren't published for free.
>

Whether or not you like it, unfortunately, this is the standard  
implemented in all recent NEC/Mitsubishi displays, and OEMs of these  
displays - these include some HP displays, all LaCie displays, as well  
as Sony Artisans.



> In the DDC information that is publicly available, I haven't seen
> any mechanism for that sort of thing. Adjusting front panel controls,
> yes. Poking memory locations, no. Can you point me at any references
> in that sort of direction ?
>
>>>     USB:
>
>> It's proprietary for sure - I wouldn't bother with them because  
>> DDC/CI is
>> definetely the better way to do it.

Not necessarily true on all displays. See USB standard referenced above.

>
> But the USB supports seemed to be "DDC over USB", so if setting RAMDAC
> values is standard on DDC, it might also be the same on USB.
> I haven't seen any references to DDC supporting such a function
> though. Do you have any pointers to information on how to
> set RAMDAC values via DDC ?
> [I found a reference for NEC/MITSUBISH to their GammaComp utility
> that seems to set gamma ramp values for their particular LCD monitors
> via DDC, but it isn't clear if this uses an proprietary extension to  
> DDC. See
> <http://www.necmitsubishi.com/support/main.cfm?thePage=http:// 
> www.necmitsubishi.com/gammacomp/body2.htm&title=GammaComp%20Download>
> ]

This protocol extension is only available from NEC under NDA.



Ben Guthro
Software Engineer
Center of Excellence for Display Technologies
a Gretag Macbeth Company
603.681.0315 x234